Since its inception in 1980, in-line skating has rapidly gained acceptance and popularity to become one of the fastest growing sports in North America and elsewhere. Each year, thousands of new in-line skaters take to this new activity as a form of fitness or recreation. Organized events such as racing, roller hockey, recreational skating and artistic skating are increasingly being staged in many neighbourhood communities.
Modelled after ice skating, in-line skating incorporates many of the traditional techniques practised in its sister sport. Ice manoeuvres such as the basic 45.degree. sideways push out, sculling, and crossover turning are all similarly performed on wheels.
To enhance the safe performance of these manoeuvres on the road, today's in-line skates are equipped with polyurethane wheels capable of maintaining good traction against the ground when the skate is in motion. In addition, these relatively soft wheels (approximately 78A durometer (hardness)) also assist in propelling the skater by generating a spring effect as the skater pushes off the skate during his/her forward stride and cushion the feel of the road.
Associated with these soft wheels however is an increase in the amount of rolling resistance. Greater effort must be expended by the skater to overcome the increased friction which causes a loss of performance particularly on straightaways. Another disadvantage inherent to the use of softer wheels is their tendency to wear out quickly. Harder wheels are therefore preferred because they reduce rolling resistance and it seems that users will sacrifice a bit of comfort for improved performance.
A compromise has been proposed by Klamer in U.S. Pat. No. 5,129,709 who discloses an in-line skate wheel having a relatively hard central core body flanked symmetrically by a pair of side wall bodies made of a softer material. Thus, when the skater is moving straight ahead purportedly substantially only the relatively hard radially outer surface of the central core will be in contact with the ground to minimize rolling resistance and increase speed. On curves however, the softer side wall bodies will contact the ground to increase traction for better grip and handling. This configuration however funnels large amounts of shock and vibration to the wheel's hub and then to the skater.
Others have proposed wheels that use a soft or relatively soft material on the outside of the wheel, and a harder material inside the wheel. The problem however is still excessive wear and torsional instability when cornering.